Environmental Engineering Reference
In-Depth Information
head at supply points or extreme head loss in the network. Here as well, the
I
r
, and
I
n
indicate more radical problem than is the case with NBI (and with
ADF
avg
and
ADF
min
).
One clear reason is that the resilience indices are products of demand driven simulations
while the NBI is calculated from PDD simulations.
3.
The resilience indices evaluate
net16
less favourably than NBI (in Figure 5.15). At the
12
th
simulation (the total pipe diameter increase of 24 %) the NBI,
ADF
avg
, and
ADF
min
all
get value 1.0 i.e. the PDD simulation indicating failures without any loss of demand,
whilst the
I
r
, and
I
n
for the same situation have values of 0.704 and 0.585, respectively;
this is considered low in view of the fact that the system operates without substantial loss
of pressure during any pipe failure.
4.
Unlike is the case with NBI, the values of
I
r
, and
I
n
, still indicate the lower reliability of
net16
compared to
net10
. The likely reason for this is the bigger surplus head of
net10
resulting from lower demand than in the case of
net16
, which can be envisaged
comparing the hydraulic performances shown in Figure 5.17. Still, the network
performance is better described by considering the value of NBI; the resilience indices
seem to be less sensitive to the change of the network layout.
1
0.9
0.8
0.7
0.6
0.5
Ir
In
NBI
ADFavg
ADFmin
0.4
0.3
0.2
0.1
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
-0.1
-0.2
-0.3
Figure 5.16
Comparison of I
r
, I
n
and NBI for increased demand of net10
1
0.9
0.8
0.7
0.6
0.5
0.4
Ir
In
NBI
ADFavg
ADFmin
0.3
0.2
0.1
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
-0.1
-0.2
-0.3
-0.4
-0.5
-0.6
-0.7
Figure 5.17
Comparison of I
r
, I
n
and NBI for increased demand of net16
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